Shipping lithium batteries in air cargo is regulated since the batteries can catch fire if they are improperly packaged, damaged, or improperly designed or assembled. For example, a United Parcel Service (UPS) airplane caught fire in 2010 and crashed on its way to Germany after arriving in Dubai from Hong Kong. The investigation into the crash by the Civil Aviation Authority (CAA) of Dubai identified the improper packaging of the batteries as the cause of the fire that preceded the crash. Because the UPS airplane contained cargo that included lithium batteries, the cargo should have been declared as hazardous.
Non-intrusive inspection systems are presently limited in their ability to detect dangerous or unsafe objects such as lithium batteries concealed in cargo. It is known in the art that images of various types of materials can be generated by using various dual-energy X-ray radiographic techniques. The intensity of transmitted X-rays provides information about the density and average atomic number (Z) of the targeted material. However, this information is not sufficient to identify, with specificity, the materials of interest present inside the target.
As a result of the image modulation based on the densities and atomic numbers of various materials, it is common for X-ray imaging systems to produce images with dark areas. Although these areas might suggest the presence of hazardous materials, they do not yield sufficient information for an operator to decide the exact nature of the imaged materials. Also, radiographs produced by conventional X-ray systems are often difficult to interpret because objects are superimposed. Therefore, a trained operator must study and interpret each image to render an opinion on the presence of a material of interest. Operator fatigue and distraction can compromise detection performance when a large number of images are to be interpreted, such as at high traffic transit points and ports. Even with automated systems, it becomes difficult to comply with the implied requirement to keep the number of false alarms low, when the system is operated at high throughputs.
One method of obtaining more useful information and clarity from X-ray imaging is using dual energy systems to measure the effective atomic numbers of materials passing through luggage, baggage, parcel, and cargo inspection areas. However, the dual energy method does not readily allow for the calculation of the actual atomic number of the concealed object itself, but rather yields only an average atomic number that represents the mix of the various items falling within the X-ray beam path, as the contents under inspection may be composed of different items and are rarely conveniently separated. Thus dual-energy analysis is often confounded.
Thus, X-ray inspection systems currently available in the art provide limited clarity for detection of materials such as lithium batteries. Accordingly, there is still a need for an improved detection system that can perform the complex task of detecting lithium batteries and distinguishing them from other types of batteries that are allowed to be transported without restriction. Such a system needs to be highly specific, so as to reliably discern materials of interest even in containers, baggage, and cargo with high clutter.